The man was convicted of murdering two people in Bangladesh in 1990 and sentenced to life imprisonment, but released in 1997 due to a "general amnesty for good behaviour".

According to papers released by the immigration tribunal, he married a British woman in March 1998 and they had three children, all UK citizens.

In 2011, ZR applied to the Home Office to come and join his family, but was refused on the grounds that his admission was "not in the public interest".

The lower immigration tribunal then backed his case under Article 8 of the European Convention on Human Rights, which protects the "right to private and family life".

But although Government lawyers could still appeal that to a higher authority, they failed to lodge the papers in time.

Refusing permission to accept a late appeal in the upper tribunal, Judge Peter King said: "I find that the application is out of time without any clear explanation for being out of time.

"I do not find that it is in the interests of justice or fairness for any extension of time to be granted. Accordingly this application is refused and time is not extended."

Conservative MP Dominic Raab, who is campaigning to reform human rights laws, told the Sunday Telegraph: "It is a damning indictment of Labour's Human Rights Act that a double murderer can claim a right to family life to skip past UK border controls designed to protect the public, and gain entry to Britain.

"Article 8 claims are making Britain a safe haven for the most dangerous foreign criminals."

Shadow immigration minister David Hanson said: "The fact is a double murderer is being let into the country because Theresa May has mismanaged her department so badly they can't meet basic deadlines.

"It is an absolute disgrace and the public will rightly be furious that after four years in the job our borders are less secure because the Home Secretary isn't paying attention to the details.

"The UK deserves better and the Home Secretary needs not only to apologise to the country for this mistake but make a commitment to improve performance so that incidents like this cannot happen again."

A Home Office spokesman said: "We are extremely disappointed with the court's decision to refuse our application to appeal, and with the original ruling allowing this individual's application on human rights grounds.

"We will continue to challenge appeals from convicted serious criminals looking for settlement in the UK, in the interests of protecting our law-abiding citizens.

"This ruling was made before new measures included in the Immigration Act came into force.

"They mean that in future, the courts will be required to have regard to Parliament's view of the public interest in immigration cases citing Article 8 - making clear the right to a family life is not to be regarded as absolute and unqualified."